Preventing corrosion of metals



Patented Dec. 4, 1951 UNITED s "rem ss PATENT OFFICE PREVENTING CORROSION OF METALS Cecil Phillips, Jr Baytown, v-'1cx.,assignor, by

mesne assignments, to Standard Oil Development Company,.' Elizabeth, N. .L, a corporation of. Delaware No Drawing. Application ."J 11ne&20,, 1947,, :Serial No. 756,112

5: Claims.

21 This invention isdirected .toa methodforsupgfpressing the corrosion -.of copper-containing .alloys in the presence .of ammonia. Specifically, :it is {directed :to .the prevention of corrosion .of

copper alloys in aqueous solutions containing ammonia.

.In many operations ,it is .often desirable-to use various types .of equipment tanks, heat 'ex- .changer and condenser tubes, valves, lines, etc.)

.-.constructed of .or containing copper :alloys .for

.handling solutions orgases containing ammonia. Such equipment usually rsufifers from-severe .cor- .rosion .or-the \copperelloys due to the chemical ..dissolution .of the copper by the. ammonia. The

.rapid destruction of the .copper alloys in conr .tact .with :solutions or -vapors containing -,ammo- .n'iaisbelive'd vto 'bedue ;to theformation of .high- Tly..soluble ,copper-ammoniumcomplex ions. The ..presence .of .oxygenis .necessary .for .the .formation of the soluble copper-ammonium ions.

Asa .result of the corrosive action of ammomiacal solutions on copper, the employers ofammonia,.such as .the petroleum refiner, must .exercise extreme care in selection .of suitable alloys .for his processing equipment. Thus, where am- .monia is .to be .used, .copper alloys are avoided However, as mentioned before, various services require ..the use of .copper .alloys on ..account of other corrosive-fluids being encountered. Thus the corrosive action of carbon dioxide in steam,

.makes nearly mandatory the employment of" copper alloys such as .an .alloy of copper,.zinc, and tin in heat exchange equipment using .corrosivesteam as .the .heat transfer medium. Thus, when ammonia'is employed in this type of equipment, rapid attack .of the copper alloy may be suffered even though the ammonia may prevent *attackof Terrousmeta'ls "by other components travelling through the equipment. Ammoniacal solutions are also widely-used in solvent extraction of hydrocarbons. Here,-.again the petroleum ra efiner must guard against allowing the-solutions to contact copper-bearing surfaces. The aforementioned corrosion reaction generally :occurs at atmospheric temperature and pressure. .It is believed that higher temperatures and pressures :mayaccelerate this reaction.

Itis, therefore, the main object of the present invention to provide a process whereby the deterioration of copper alloys in the presence of ammonia is substantially eliminated.

Another object of the invention is to provide a method whereby copper alloys may be employed in services where they are exposed to ammoniacal solutions.

The objects of the present invention are achieved by maintaining in corrosive ammoniacal solutions in contact with copper and its alloys at corrosion inhibiting amount of a salt of a petroleum sulfonic acid.

Briefly, the present invention involve the B0 soluble sulfonic acids. :acids may befreed of water and "then converted ..into :the corresponding .salts .by addition of sodi- ,ployed to --:pr0iduce the salts used in the present invention :may be obtained in :a manner well known to theart. The production of mahogany .sulfonicacidshas .been disclosed widely inpatent literature. Howeven'a conventional method for preparing these-acids involves .the treatment with concentrated sulfuric acid 10f .a zfeed stock comprising a substantial portion of unsaturated cyclic hydrocarbons. Exemplary of the type of feed :stocks =which:may:be used *are thesolvent 'extracts resulting :from .solvent extraction 'of -a distillate boiling in the :lubricating ioil boiling range, such as, for example, ..-a :phenolextract. The :extract layer, upon treatment with strong sulfuric acid results in the formation of a layer comprising oil and oil soluble sulfonic acids -or mahogany acids, and a second layercomprising sludge: par- .ticles and 'water soluble :sulfonic acids. These two layers .ar then separated .under the influence :of gravity and the oil layer, including mahogany .acids, is treated with successive ,portions of water to obtain .the predominately oil These .oil .soluble sulfon-ic .um hydroxide or ammonium hydroxide if desired. As a specific example, a distillate obtained .from a naphthenic crude oil may be solvent extracted with a solvent having .the characteristics of furfural or phenolsand theextract brought in .con-

tact with sulfuric acid of approximately 98% concentration. Upon, contacting the concentrated sulfuric :acid with the petroleum extract,

sulfonic-racids are formed. Thenmahoganyacids remain intthe oilrphase whichseparates from the acid phase.

In applying the-concentrated .sulfuric .acid,.it is customary to divide the total amount employed into a number of portions and treat the petroleum extract separately with each portion and the mahogany acids allowed to remain in the extract phase or separated, if desired, be-

tween each treat with sulfuric acid. Preferably the oil soluble sulfonic acids or mahogany acids are obtained from the acid treated extract after each portion of sulfuric acid has been added thereto.

ing the corrosion of copper alloys by ammonia is not understood, but it is believed to be due to the formation of a very thin protective film on the metal. It is understood, ofcourse, that I do not wish to bind myself to any theory offered as an explanation of the beneficial effect.

An advantage of the process of the present invention, irrespective of the prevention of corrosion of copper and its alloys, is the ability to use existing equipment in which copper and its alloys are present in processes involving the use of ammonia.

- In order to illustrate the beneficial effects of this invention, specimens of copper-containing metal (70% copper, 29% zinc, and 1% tin) were immersed in aqueous solutions of ammonia.

These tests were in progress for 24 hours at room temperature and atmospheric pressure, Air was bubbled through the ammonia solutions throughout the tests. These tests were repeated under identical conditions .with small amounts of sodium sulfonates of petroleum sulfonic acids of the type illustrated added to the aqueous solutions of ammonia. The results obtained in these tests are shown in the following table:

It will be observed from the data presented in the foregoing table that the addition of small amounts of sodium salts of petroleum sulfonic acids effects marked reductions in the tendencies of aqueous solutions of ammonia to corrode copper-containing alloys.

Another series of runs identical to those described in the foregoing paragraph was conducted in which specimens of the same type of copper-containing metal were immersed in aqueous solutions of ammonia to which were added small amounts of ammonium sulfonates of mahogany acids from petroleum. All conditions in this series of runs otherwise were identical to the series of runs in which sodium sulfonates of mahogany acids were employed. The results obtained in these runs are shown in the following table:

It will be observed from the data presented in the foregoing table that the addition of small amounts of ammonium salts of petroleum sulfonic acids effects marked reductions in the tendencies of aqueous solutions of ammonia to corrode copper-bearing alloys.

The present invention has been described and illustrated as inhibiting the corrosive effect of solutions in ammonia and water. It is understood that the invention has broad application in the inhibition of corrosive action of an ammoniacal solution such as ammonia and water to copper-bearing metals. The invention may be applied to the inhibition of the corrosive effects ,of aqueous solutions of ammonium salts. For example, ammonium acetate is widely used in the petroleum refinery as a solvent. It 'is known that ammonium acetate will attack ,copper-bearing metals quite readily; Thereforejit is within the spirit and scope of the invention to inhibit the corrosiveness of ammonium salt solutions to copper-bearing metals employing salts of mahogany acids as the inhibitor.

The nature and objects of the present invention having been fully described and illustrated, what I wish to claim as new and useful andto secure by Letters Patent is: g

1. A method for reducing the corrosive action of a corrosive solution including ammonia, water, and oxygen to an article having a corrodible surface consisting of copper, tin, and zinc in contact with said. solution which comprises introducing into said solution an amount of a salt of a petroleum mahogany acid suificient to inhibit the corrosion thereof.

2. A method in accordance with claim 1 in which the amount of salt of mahogany acids is in the range between 0.001% and 5% by weight of the corrosive solution.

3. A method in accordance with claim 1 in which the salt of mahogany acid is a sodium salt.

4. A method in accordance with claim 1 in which the salt of mahogany acid is a potassium salt.

5. A method in .accordance with claim 1 in which .the salt of mahogany acid is an ammonium salt.

CECIL PHILLIPS, JR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,630,101 Wilkin May 24, 1927 2,081,168 De Mering May 25, 1937 2,238,651 Keenen Apr. 15, 1941 2,349,785 v Faust May 23, 1944 2,445,936 Butcosk July 27, 1948 2,455,659

Duncan et al Dec. 7, 1948 

1. A METHOD FOR REDUCING THE CORROSIVE ACTION OF A CORROSIVE SOLUTION INCLUDING AMMONIA, WATER, AND OXYGEN TO AN ARTICLE HAVING A CORRODIBLE SURFACE CONSISTING OF COPPER, TIN, AND ZINC IN CONTACT WITH SAID SOLUTION WHICH COMPRISES INTRODUCING INTO SAID SOLUTION AN AMOUNT OF A SALF OF A PETROLEUM MAHOGANY ACID SUFFICENT TO INHIBIT THE CORROSIVE THEREOF. 